Abstract
Scavenger receptor class B, type I (SR-BI) is expressed in the intestines of rodents and has been suggested to be involved in the absorption of dietary cholesterol. The aim of this study was to determine whether intestinal SR-BI expression is affected in animal models with altered bile delivery to the intestine and impaired cholesterol absorption. SR-BI protein and mRNA levels were determined in proximal and distal small intestine from control, bile-duct-ligated and bile-diverted rats and from control and bile-duct-ligated mice. Two genetically altered mouse models were studied: multidrug resistance-2 P-glycoprotein-deficient [Mdr2((-/-))] mice that produce phospholipid/cholesterol-free bile, and cholesterol 7 alpha -hydroxylase-deficient [Cyp7a((-/-))] mice, which exhibit qualitative and quantitative changes in the bile-salt pool. Cholesterol-absorption efficiency was quantified using a dual-isotope ratio method. SR-BI was present at the apical membrane of enterocytes in control rats and mice and was more abundant in proximal than in distal segments of the intestine. In bile-duct-ligated animals, levels of SR-BI protein were virtually absent and mRNA levels were decreased by approximate to 50 %. Bile-diverted rats, Mdr2((-/-)) mice and Cyp7a((-/-)) mice showed decreased levels of intestinal SR-BI protein while mRNA levels were unaffected. Cholesterol absorption was reduced by > 90% in bile-duct-ligated and bile-diverted animals and in Cyp7a((-/-)) mice, whereas Mdr2((-/-)) mice showed an approximate to 50% reduction. This study shows that SR-BI is expressed at the apical membrane of enterocytes of rats and mice; mainly in the upper intestine where cholesterol absorption is greatest, and indicates that bile components play a role in post-transcriptional regulation of SR-BI expression. Factors associated with cholestasis appear to be involved in transcriptional control of intestinal SR-BI expression. The role of SR-BI in the cholesterol-absorption process remains to be defined.
| Original language | English |
|---|---|
| Pages (from-to) | 317-325 |
| Number of pages | 9 |
| Journal | Biochemical Journal |
| Volume | 356 |
| Publication status | Published - 1-Jun-2001 |
Keywords
- absorption
- bile salts
- cholesterol
- knockout mouse
- phospholipid
- DENSITY-LIPOPROTEIN RECEPTOR
- CHOLESTEROL 7-ALPHA-HYDROXYLASE GENE
- PHYSICAL-CHEMICAL BEHAVIOR
- PLASMA RATIO METHOD
- ADULT HUMAN-BEINGS
- DIETARY-CHOLESTEROL
- BILIARY CHOLESTEROL
- AGGREGATION STATES
- LINOLEIC-ACID
- HDL RECEPTOR